HYPSOMETRICAL RELATIONS OF LOWER TARIM BASIN AND OF KURUK-DARJA. 577
In general there exists a great and beautiful agreement between the contour-lines of the Tarim and those of the Kontsche-darja and the Kuruk-darja. The contour-line of 82o m. may be said to form the boundary between the true Lop region, with the depression of Kara-koschun to the south and that of Lop-nor to the north. For the course of the contour-lines in the western part of the interior of the desert there is nothing better to build upon than conjecture, for nobody has ever been there. The altitude 802 m. shown in my itinerary across the desert in 1900 may be regarded as improbable, even though the advance of the desert lakes in that direction does point to the presence of low-lying country. It is interesting to observe, that the altitude 8o8 m. occurs precisely at the spot in which the Chinese maps place the Lop-nor, as also almost exactly opposite to the lowest part of the crossing I made in 1901, where the camping-ground at 815.3 m. is indicated. From my surveyed line alone no conclusion can be drawn with regard to the exact position of the Lop-nor, that is to say, it is impossible to determine whether this line crosses the eastern or the western part of the old lake basin. Nevertheless there exist several circumstances which suggest that the greater part of the lake-basin lay west of the line surveyed, and that this line consequently crosses the eastern portion of the Lop-nor, where the lake was relatively narrow. Hence the basins of the old lake as shown on Pl. 37 have turned out smaller than they ought to be, that is in relation to the Kara-koschun. The picture which the Chinese maps give of Lop-nor, the situation of the Kara-koschun, the flow of the water of Kara-koschun towards the north-northeast — all indicate that the greater part of the Lop-nor lay west of the line I levelled, the other properties of which, as well as the lessons it has to teach us, I have already dwelt on in the preceding pages. But the contour-lines from meter to meter which I have inserted on Pl. 59 are however only approximately trustworthy. Along the levelled line I did not consider it necessary for this purpose to make use of any other altitudes except those which coincide with the seven camps we made. Further, I have divided the old Lop depression into two basins, the southern one containing the Lop-nor proper and the northern one the three small lakes shown on the Wu-tschang map. Yet it is not this map alone which corroborates the correctness of the conception. The relative swelling, on which the ruins of Lôu-lan are situated, would appear to project westwards between these two basins. Further, we find close to the foot of the mountains two points with altitudes of 81 o m., which, altogether independently 'of the Chinese maps, would have forced us to push back the contours towards the north. How far it is an actual elevation of the ground which separates these two depressions from one another it is difficult to say; in that case it will certainly have been pierced in one or even several places by canals from the small lakes, to communicate with the great Lop-nor. The flow of the water towards the north-north-east renders it necessary to posit the existence of a connecting-channel between the two lake-basins, the Kara-koschun and the Lop-nor. On the map I have shown the former, the southern lake, as though it contained no water. The lowest point that I sounded in its basin lies at an absolute altitude of
8 r m.
I have said, that notwithstanding the abundant detail in the points measured hypsometrically along my surveyed line, this latter appears on Pl. 59 delineated with
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